Alkylation of aromatic compound with normal olefins using aluminum chloride-lewis base catalyst



United States Patent 3,365,509 ALKYLATION OF AROMATIC COMPOUND WITH NORMAL OLEFINS USING ALUMINUM CHLO- RIDE-LEWIS BASE CATALYST John J. Shook, Oakland, Calif., assignor to Chevron Research Company, San Francisco, Calif., a corporation of Delaware N0 Drawing. Filed Nov. 8, 1965, Ser- No. 506,870 10 Claims. (Cl. 260-671) The present invention relates to the alkylation of an aromatic compound. More particularly, the invention relates to alkylating an aromatic compound, such as benzene, with a straight chain olefin having 9 to 20 carbon atoms while controlling the position of attachment of the aryl group to the alkyl chain and thus produce a mixture having a desirably modified distribution of aryl alkane isomers. The resulting alkylate is convertible to valuable surface-active agents by sulfonation, and neutralization with a base, such as sodium hydroxide.

It is known that specific propertie of a detergent depend on the structure of the alkyl aryl hydrophobic group contained in the detergent. For example, the rate of biodegradation of alkyl aromatics in which the alkyl groups are of straight chain structure is related to the isomeric nature of the aryl alkanes; that is, the greater the number of carbon atoms between the terminal alkyl group and the carbon to which the benzene is attached, the more susceptible is the material to oxidation by bacteria. Studies have shown that the 2-phenyl isomer is most rapidly degraded, followed by the 3-, 4- and S-phenyl isomers (see R. L. Huddleston and R. C. Allred, Developments in Industrial Microbiology, vol. 4, p. 24 (1963)). On the other hand, the internal isomers, that is, the 4-, 5- and 6-phenyl isomers, have been shown to have better wetting and washing properties in certain applications, such as the washing of dishes.

It is also known that regardless of the particular species of normal olefin used in the alkylation reaction with regard to the position of the double bond in the chain, whether between the first or second carbon atoms, as represented by the alpha olefins, or in a more central position, as represented by normal dodecene-6, isomerization occurs so that a mixture of aryl alkanes is obtained in which the aryl group is attached not only to a carbon atom of the double bond of the original olefin, but also to a different carbon atom somewhere else in the chain. Isomerization of normal olefins, whereby molecular species differing in position of the attachment of the aryl group to the alkyl chain, is quite pronounced in AlCl catalyzed alkylation reactions involving an alkylatable aryl compound, such as benzene, toluene, ethyl benzene, xylene or phenol, with normal olefins of 9 to 2-0 carbon atoms.

For example, alkylation under the usual conditions, namely, 0.1 mol A101 2 mols dodecene-l and 10 mols benzene at a temperature of 30 C. and 50 C. produced Patented Jan. 23, 1968 a mixture of secondary phenyl alkanes having the following constitution, in weight percent In accordance with the present invention it has been found that if the alkylation of aryl hydrocarbon and C C olefin is conducted using anhydrous AlCl catalyst in the presence of a small amount of a Lewis base, the isomer distribution of the final alkylate product is desirably modified. Thus, with the alpha olefins the amount of 2-phenyl alkanes is increased at the expense of the internal isomers; with internal olefins, such as 6-dodecene, the amount of internal isomers, such as 4-, 5- and 6-phenyl isomers, is increased.

Usual conditions of alkylation can be used in the present invention to alkylate a suitable mononuclear aromatic compound, e.g., benzene or toluene, with a straight-chain olefin of 9 to 20 carbon atoms. In general, there will be employed an excess of the aromatic compound to ensure monoalkylation, i.e., attachment of the aryl compound to only one molecule of alkylating agent; 1 to 20 mols, preferably 3 to 10 mols, of aromatic compound, e.g., benzene, for each mol of olefin represents a satisfactory range. The amount of anhydrous AlCl catalyst can range from 0.5 to 20 weight percent, preferably 1 to 10 weight percent, based on olefin; and the Lewis base, 1 to 100 mol percent, preferably 5 to 25 mol percent of the AlCl Reaction temperatures can vary from 0 C. to C., preferably 5 to 50 C.

Following the alkylation reaction, the alkylate product is isolated in normal fashion. The catalyst is separated from the reaction mixture, and the organic phase containing the alkylate is washed free of any entrained catalyst with water and caustic. Excess unreacted aromatic is removed, and the desired product is obtained by fractional distillation.

Lewis bases are well known substances. They are defined as materials containing a pair of unshared electrons. For the purposes of the present invention they can also be characterized as being soluble in the reaction mixture. Compounds containing trivalent nitrogen and phosphorous or divalent oxygen and sulfur are examples of the Lewis bases; these include ethers, amines, amides, and sulfides, more specific examples being diethyl ether, n-dodecylamine, and dimethylformamide.

As illustrative of the invention, there are tabulated below a number of experiments involving the alkylation of benzene with n-dodecene-l. Except where indicated, there were used 1.5 mols benzene, 0.3 mol l-dodecene, and 2.0 g. anhydrous granular AlCl Analysis of the alkylate to determine isomeric distribution was performed using gas-liquid chromatography and mass spectrometry.

Industrial and Engineer-in Chemistr vol. 52 S3"- 836 1900). g y pp 0 PHENYLDODECANE ISOMER DISTRIBUTIONS i Isomer Distribution (Percent) Ratio, Example Reaction Conditions "0 Yield of 2+3 Alkylate 4 t as w M 1 No Lewis base 30 68 3 22 16 15 15 1. 8 2- 5 92 36 23 17 12 12 2. 4 3 25 93 4O 22 15 12 11 2. 7 4-- 6 94 48 23 12 11 7 3. 9 5 o 25 49 21 11 11 8 3,7 6 0.7 ml. dimethyltormamide 7 87 48 20 l2 l3 7 2. 4 7.. 0.25 ml. diethyl ether 7 91 50 23 11 10 6 4. 6 8% do 7 25 60 20 8 7 5 6.7 9 0.25 ml. n-dodeeylamine 25 94 50 0 1 l3 7 3. 5

2 Reaction run using 3.0 mols benzene, 0.15 mol l-dodecene, and 2.0 g. anhydrous granular aluminum chloride;

It is shown in the table that, by carrying out the alkylation reaction in the presence of a Lewis base, the Z-phenyl alkane content can be increased by about 56%, as shown by a comparison of Experiments 1 and 9. The Z-phenyl alkane content can be increased by almost 90%, as shown in Experiment 8. In all experiments performed in accordance with the invention, the ratio of the sum of the 2- and S-phenyl alkane isomers to the sum of the more internal isomers is higher than that which prevails when AlCl alone is used. In addition, the table shows the overall yield of alkylate is higher.

I claim:

1. In the process of alkylating an alkylatable mononuclear aromatic compound with a normal olefin of 9 to 20 carbon atoms by the A101 alkylation reaction to produce a mixture of secondary aryl alkane isomers, said mixture being useful in the preparation of detergents, the improvement of controlling the isomer distribution of said mixture, which comprises carrying out the alkylation reaction with AlCl catalyst and 1 to 100%, based on the AlCl of a Lewis base soluble in the reaction mixture.

2. Process according to claim 1, wherein the mononuclear aromatic compound is benzene.

-3. In the process of alkylating an alkylatable mononuclear aromatic compound with normal alpha olefins of about 9 to 20 carbon atoms, by the AlCl catalyzed alkylation reaction to produce a mixture of secondary aryl alkane isomers, including the 2'aryl alkane isomer, said mixture being useful as a detergent intermediate, the improvement of increasing the proportion of the 2-aryl alkane isomers in said mixture which comprises carrying out the alkylation reaction with AlCl catalyst in the presence of a small amount of a Lewis base soluble in the reaction mixture.

4. Process according to claim 3, wherein the mononuclear aromatic compound is benzene.

5. Process according to claim 3, wherein the Lewis base is present in an amount of about 1 to mol percent of the AlCl catalyst.

6. Process according to claim 5, wherein the mononuclear aromatic compound is benzene.

7. Process according to claim '6, wherein the Lewis base is dimethylformamide.

8. Process according to claim 6, wherein the Lewis base is diethyl ether.

9. Process according to claim 6, wherein the Lewis base is n-dodecylamine.

10. Process according to claim 6, wherein the Lewis base is present in an amount of 5 to 25 mol percent of the A101 References Cited UNITED STATES PATENTS 3,248,443 4/1966 McEwan et al 260671 DELBERT E. GANTZ, Primary Examiner.

C. R. DAVIS, Assistant Examiner. 

1. IN THE PROCESS OF ALKYLATING AN ALKYLATABLE MONONUCLEAR AROMATIC COMPOUND WITH A NORMAL OLEFIN OF 9 TO 20 CARBON ATOMS BY THE ALCL3 ALKYLATION REACTION TO PRODUCE A MIXTURE OF SECONDARY ARYL ALKANE ISOMERS, SAID MIXTURE BEING USEFUL IN THE PREPARATION OF DETERGENTS, THE IMPROVEMENT OF CONTROLLING THE ISOMER DISTRIBUTION OF SAID MIXTURE, WHICH COMPRISES CARRYING OUT THE ALKYLATION REACTION WITH ALCL3, CATALYST AND 1 TO 100%, BASED ON THE ALCL3, OF A LEWIS BASE SOLUBLE IN THE REACTION MIXTURE. 